using System;
using System.Diagnostics;
using System.Text;

using Bitmask = System.UInt64;
using i64 = System.Int64;
using u32 = System.UInt32;
using u64 = System.UInt64;
namespace CS_SQLite3
{
#if !NO_TCL
  using tcl.lang;
  using Tcl_Interp = tcl.lang.Interp;
  using Tcl_Obj = tcl.lang.TclObject;
  using Tcl_CmdInfo = tcl.lang.Command;
  using Tcl_DString = tcl.lang.TclString;

  using sqlite3_int64 = System.Int64;
  using sqlite3_u3264 = System.UInt64;
  using sqlite3_stmt = csSQLite.Vdbe;
  using sqlite3_value = csSQLite.MemRef;

  public partial class csSQLite
  {
    /*
    ** 2008 Jan 22
    **
    ** The author disclaims copyright to this source code.  In place of
    ** a legal notice, here is a blessing:
    **
    **    May you do good and not evil.
    **    May you find forgiveness for yourself and forgive others.
    **    May you share freely, never taking more than you give.
    **
    ******************************************************************************
    **
    ** This file contains code for a VFS layer that acts as a wrapper around
    ** an existing VFS. The code in this file attempts to verify that SQLite
    ** correctly populates and syncs a journal file before writing to a
    ** corresponding database file.
    **
    ** $Id: test_journal.c,v 1.17 2009/06/26 10:39:36 danielk1977 Exp $
    **
    *************************************************************************
    **  Included in SQLite3 port to C#-SQLite;  2008 Noah B Hart
    **  C#-SQLite is an independent reimplementation of the SQLite software library
    **
    **  $Header$
    *************************************************************************
    */
#if SQLITE_TEST          //* This file is used for testing only */

    //#include "sqlite3.h"
    //#include "sqliteInt.h"

    /*
    ** INTERFACE
    **
    **   The public interface to this wrapper VFS is two functions:
    **
    **     jt_register()
    **     jt_unregister()
    **
    **   See header comments associated with those two functions below for
    **   details.
    **
    ** LIMITATIONS
    **
    **   This wrapper will not work if "PRAGMA synchronous = off" is used.
    **
    ** OPERATION
    **
    **  Starting a Transaction:
    **
    **   When a write-transaction is started, the contents of the database is
    **   inspected and the following data stored as part of the database file
    **   handle (type struct jt_file):
    **
    **     a) The page-size of the database file.
    **     b) The number of pages that are in the database file.
    **     c) The set of page numbers corresponding to free-list leaf pages.
    **     d) A check-sum for every page in the database file.
    **
    **   The start of a write-transaction is deemed to have occurred when a
    **   28-byte journal header is written to byte offset 0 of the journal
    **   file.
    **
    **  Syncing the Journal File:
    **
    **   Whenever the xSync method is invoked to sync a journal-file, the
    **   contents of the journal file are read. For each page written to
    **   the journal file, a check-sum is calculated and compared to the
    **   check-sum calculated for the corresponding database page when the
    **   write-transaction was initialized. The success of the comparison
    **   is assert()ed. So if SQLite has written something other than the
    **   original content to the database file, an assert() will fail.
    **
    **   Additionally, the set of page numbers for which records exist in
    **   the journal file is added to (unioned with) the set of page numbers
    **   corresponding to free-list leaf pages collected when the
    **   write-transaction was initialized. This set comprises the page-numbers
    **   corresponding to those pages that SQLite may now safely modify.
    **
    **  Writing to the Database File:
    **
    **   When a block of data is written to a database file, the following
    **   invariants are asserted:
    **
    **     a) That the block of data is an aligned block of page-size bytes.
    **
    **     b) That if the page being written did not exist when the
    **        transaction was started (i.e. the database file is growing), then
    **        the journal-file must have been synced at least once since
    **        the start of the transaction.
    **
    **     c) That if the page being written did exist when the transaction
    **        was started, then the page must have either been a free-list
    **        leaf page at the start of the transaction, or else must have
    **        been stored in the journal file prior to the most recent sync.
    **
    **  Closing a Transaction:
    **
    **   When a transaction is closed, all data collected at the start of
    **   the transaction, or following an xSync of a journal-file, is
    **   discarded. The end of a transaction is recognized when any one
    **   of the following occur:
    **
    **     a) A block of zeroes (or anything else that is not a valid
    **        journal-header) is written to the start of the journal file.
    **
    **     b) A journal file is truncated to zero bytes in size using xTruncate.
    **
    **     c) The journal file is deleted using xDelete.
    */

#if TODO_SKIP_FOR_NOW
/*
** Maximum pathname length supported by the jt backend.
*/
//#define JT_MAX_PATHNAME 512

/*
** Name used to identify this VFS.
*/
//#define JT_VFS_NAME "jt"

typedef struct jt_file jt_file;
struct jt_file {
sqlite3_file base;
const char *zName;       /* Name of open file */
int flags;               /* Flags the file was opened with */

/* The following are only used by database file file handles */
int eLock;               /* Current lock held on the file */
u32 nPage;               /* Size of file in pages when transaction started */
u32 nPagesize;           /* Page size when transaction started */
Bitvec *pWritable;       /* Bitvec of pages that may be written to the file */
u32 *aCksum;             /* Checksum for first nPage pages */
int nSync;               /* Number of times journal file has been synced */

/* Only used by journal file-handles */
sqlite3_int64 iMaxOff;   /* Maximum offset written to this transaction */

jt_file *pNext;          /* All files are stored in a linked list */
sqlite3_file *pReal;     /* The file handle for the underlying vfs */
};

/*
** Method declarations for jt_file.
*/
static int jtClose(sqlite3_file*);
static int jtRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
static int jtWrite(sqlite3_file*,const void*,int iAmt, sqlite3_int64 iOfst);
static int jtTruncate(sqlite3_file*, sqlite3_int64 size);
static int jtSync(sqlite3_file*, int flags);
static int jtFileSize(sqlite3_file*, sqlite3_int64 *pSize);
static int jtLock(sqlite3_file*, int);
static int jtUnlock(sqlite3_file*, int);
static int jtCheckReservedLock(sqlite3_file*, int *);
static int jtFileControl(sqlite3_file*, int op, void *pArg);
static int jtSectorSize(sqlite3_file*);
static int jtDeviceCharacteristics(sqlite3_file*);

/*
** Method declarations for jt_vfs.
*/
static int jtOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
static int jtDelete(sqlite3_vfs*, const char *zName, int syncDir);
static int jtAccess(sqlite3_vfs*, const char *zName, int flags, int *);
static int jtFullPathname(sqlite3_vfs*, const char *zName, int, char *zOut);
static void *jtDlOpen(sqlite3_vfs*, const char *zFilename);
static void jtDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
static void (*jtDlSym(sqlite3_vfs*,void*, const char *zSymbol))(void);
static void jtDlClose(sqlite3_vfs*, void*);
static int jtRandomness(sqlite3_vfs*, int nByte, char *zOut);
static int jtSleep(sqlite3_vfs*, int microseconds);
static int jtCurrentTime(sqlite3_vfs*, double*);

static sqlite3_vfs jt_vfs = {
1,                             /* iVersion */
sizeof(jt_file),               /* szOsFile */
JT_MAX_PATHNAME,               /* mxPathname */
0,                             /* pNext */
JT_VFS_NAME,                   /* zName */
0,                             /* pAppData */
jtOpen,                        /* xOpen */
jtDelete,                      /* xDelete */
jtAccess,                      /* xAccess */
jtFullPathname,                /* xFullPathname */
jtDlOpen,                      /* xDlOpen */
jtDlError,                     /* xDlError */
jtDlSym,                       /* xDlSym */
jtDlClose,                     /* xDlClose */
jtRandomness,                  /* xRandomness */
jtSleep,                       /* xSleep */
jtCurrentTime                  /* xCurrentTime */
};

static sqlite3_io_methods jt_io_methods = {
1,                             /* iVersion */
jtClose,                       /* xClose */
jtRead,                        /* xRead */
jtWrite,                       /* xWrite */
jtTruncate,                    /* xTruncate */
jtSync,                        /* xSync */
jtFileSize,                    /* xFileSize */
jtLock,                        /* xLock */
jtUnlock,                      /* xUnlock */
jtCheckReservedLock,           /* xCheckReservedLock */
jtFileControl,                 /* xFileControl */
jtSectorSize,                  /* xSectorSize */
jtDeviceCharacteristics        /* xDeviceCharacteristics */
};

struct JtGlobal {
sqlite3_vfs *pVfs;             /* Parent VFS */
jt_file *pList;                /* List of all open files */
};
static struct JtGlobal g = {0, 0};

/*
** Functions to obtain and relinquish a mutex to protect g.pList. The
** STATIC_PRNG mutex is reused, purely for the sake of convenience.
*/
static void enterJtMutex(void){
sqlite3_mutex_enter(sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_PRNG));
}
static void leaveJtMutex(void){
sqlite3_mutex_leave(sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_PRNG));
}

extern int sqlite3_io_error_pending;
extern int sqlite3_io_error_hit;
static void stop_ioerr_simulation(int *piSave, int *piSave2){
*piSave = sqlite3_io_error_pending;
*piSave2 = sqlite3_io_error_hit;
sqlite3_io_error_pending = -1;
sqlite3_io_error_hit = 0;
}
static void start_ioerr_simulation(int iSave, int iSave2){
sqlite3_io_error_pending = iSave;
sqlite3_io_error_hit = iSave2;
}

/*
** The jt_file pointed to by the argument may or may not be a file-handle
** open on a main database file. If it is, and a transaction is currently
** opened on the file, then discard all transaction related data.
*/
static void closeTransaction(jt_file *p){
sqlite3BitvecDestroy(p->pWritable);
//sqlite3_free(p->aCksum);
p->pWritable = 0;
p->aCksum = 0;
p->nSync = 0;
}

/*
** Close an jt-file.
*/
static int jtClose(sqlite3_file *pFile){
jt_file **pp;
jt_file *p = (jt_file *)pFile;

closeTransaction(p);
enterJtMutex();
if( p->zName ){
for(pp=&g.pList; *pp!=p; pp=&(*pp)->pNext);
*pp = p->pNext;
}
leaveJtMutex();
return sqlite3OsClose(p->pReal);
}

/*
** Read data from an jt-file.
*/
static int jtRead(
sqlite3_file *pFile,
void *zBuf,
int iAmt,
sqlite_int64 iOfst
){
jt_file *p = (jt_file *)pFile;
return sqlite3OsRead(p->pReal, zBuf, iAmt, iOfst);
}

/*
** Parameter zJournal is the name of a journal file that is currently
** open. This function locates and returns the handle opened on the
** corresponding database file by the pager that currently has the
** journal file opened. This file-handle is identified by the
** following properties:
**
**   a) SQLITE_OPEN_MAIN_DB was specified when the file was opened.
**
**   b) The file-name specified when the file was opened matches
**      all but the final 8 characters of the journal file name.
**
**   c) There is currently a reserved lock on the file.
**/
static jt_file *locateDatabaseHandle(const char *zJournal){
jt_file *pMain = 0;
enterJtMutex();
for(pMain=g.pList; pMain; pMain=pMain->pNext){
int nName = strlen(zJournal) - strlen("-journal");
if( (pMain->flags&SQLITE_OPEN_MAIN_DB)
&& (strlen(pMain->zName)==nName)
&& 0==memcmp(pMain->zName, zJournal, nName)
&& (pMain->eLock>=SQLITE_LOCK_RESERVED)
){
break;
}
}
leaveJtMutex();
return pMain;
}

/*
** Parameter z points to a buffer of 4 bytes in size containing a
** unsigned 32-bit integer stored in big-endian format. Decode the
** integer and return its value.
*/
static u32 decodeUint32(const unsigned char *z){
return (z[0]<<24) + (z[1]<<16) + (z[2]<<8) + z[3];
}

/*
** Calculate a checksum from the buffer of length n bytes pointed to
** by parameter z.
*/
static u32 genCksum(const unsigned char *z, int n){
int i;
u32 cksum = 0;
for(i=0; i<n; i++){
cksum = cksum + z[i] + (cksum<<3);
}
return cksum;
}

/*
** The first argument, zBuf, points to a buffer containing a 28 byte
** serialized journal header. This function deserializes four of the
** integer fields contained in the journal header and writes their
** values to the output variables.
**
** SQLITE_OK is returned if the journal-header is successfully
** decoded. Otherwise, SQLITE_ERROR.
*/
static int decodeJournalHdr(
const unsigned char *zBuf,         /* Input: 28 byte journal header */
u32 *pnRec,                        /* Out: Number of journalled records */
u32 *pnPage,                       /* Out: Original database page count */
u32 *pnSector,                     /* Out: Sector size in bytes */
u32 *pnPagesize                    /* Out: Page size in bytes */
){
unsigned char aMagic[] = { 0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd7 };
if( memcmp(aMagic, zBuf, 8) ) return SQLITE_ERROR;
if( pnRec ) *pnRec = decodeUint32(&zBuf[8]);
if( pnPage ) *pnPage = decodeUint32(&zBuf[16]);
if( pnSector ) *pnSector = decodeUint32(&zBuf[20]);
if( pnPagesize ) *pnPagesize = decodeUint32(&zBuf[24]);
return SQLITE_OK;
}

/*
** This function is called when a new transaction is opened, just after
** the first journal-header is written to the journal file.
*/
static int openTransaction(jt_file *pMain, jt_file *pJournal){
unsigned char *aData;
sqlite3_file *p = pMain->pReal;
int rc = SQLITE_OK;

aData = sqlite3_malloc(pMain->nPagesize);
pMain->pWritable = sqlite3BitvecCreate(pMain->nPage);
pMain->aCksum = sqlite3_malloc(sizeof(u32) * (pMain->nPage + 1));
pJournal->iMaxOff = 0;

if( !pMain->pWritable || !pMain->aCksum || !aData ){
rc = SQLITE_IOERR_NOMEM;
}else if( pMain->nPage>0 ){
u32 iTrunk;
int iSave;
int iSave2;

stop_ioerr_simulation(&iSave, &iSave2);

/* Read the database free-list. Add the page-number for each free-list
** leaf to the jt_file.pWritable bitvec.
*/
rc = sqlite3OsRead(p, aData, pMain->nPagesize, 0);
iTrunk = decodeUint32(&aData[32]);
while( rc==SQLITE_OK && iTrunk>0 ){
u32 nLeaf;
u32 iLeaf;
sqlite3_int64 iOff = (iTrunk-1)*pMain->nPagesize;
rc = sqlite3OsRead(p, aData, pMain->nPagesize, iOff);
nLeaf = decodeUint32(&aData[4]);
for(iLeaf=0; rc==SQLITE_OK && iLeaf<nLeaf; iLeaf++){
u32 pgno = decodeUint32(&aData[8+4*iLeaf]);
sqlite3BitvecSet(pMain->pWritable, pgno);
}
iTrunk = decodeUint32(aData);
}

/* Calculate and store a checksum for each page in the database file. */
if( rc==SQLITE_OK ){
int ii;
for(ii=0; rc==SQLITE_OK && ii<pMain->nPage; ii++){
i64 iOff = (i64)(pMain->nPagesize) * (i64)ii;
if( iOff==PENDING_BYTE ) continue;
rc = sqlite3OsRead(pMain->pReal, aData, pMain->nPagesize, iOff);
pMain->aCksum[ii] = genCksum(aData, pMain->nPagesize);
}
}

start_ioerr_simulation(iSave, iSave2);
}

//sqlite3_free(aData);
return rc;
}

/*
** The first argument to this function is a handle open on a journal file.
** This function reads the journal file and adds the page number for each
** page in the journal to the Bitvec object passed as the second argument.
*/
static int readJournalFile(jt_file *p, jt_file *pMain){
int rc = SQLITE_OK;
unsigned char zBuf[28];
sqlite3_file *pReal = p->pReal;
sqlite3_int64 iOff = 0;
sqlite3_int64 iSize = p->iMaxOff;
unsigned char *aPage;
int iSave;
int iSave2;

aPage = sqlite3_malloc(pMain->nPagesize);
if( !aPage ){
return SQLITE_IOERR_NOMEM;
}

stop_ioerr_simulation(&iSave, &iSave2);

while( rc==SQLITE_OK && iOff<iSize ){
u32 nRec, nPage, nSector, nPagesize;
u32 ii;

/* Read and decode the next journal-header from the journal file. */
rc = sqlite3OsRead(pReal, zBuf, 28, iOff);
if( rc!=SQLITE_OK
|| decodeJournalHdr(zBuf, &nRec, &nPage, &nSector, &nPagesize)
){
goto finish_rjf;
}
iOff += nSector;

if( nRec==0 ){
/* A trick. There might be another journal-header immediately
** following this one. In this case, 0 records means 0 records,
** not "read until the end of the file". See also ticket #2565.
*/
if( iSize>=(iOff+nSector) ){
rc = sqlite3OsRead(pReal, zBuf, 28, iOff);
if( rc!=SQLITE_OK || 0==decodeJournalHdr(zBuf, 0, 0, 0, 0) ){
continue;
}
}
nRec = (iSize-iOff) / (pMain->nPagesize+8);
}

/* Read all the records that follow the journal-header just read. */
for(ii=0; rc==SQLITE_OK && ii<nRec && iOff<iSize; ii++){
u32 pgno;
rc = sqlite3OsRead(pReal, zBuf, 4, iOff);
if( rc==SQLITE_OK ){
pgno = decodeUint32(zBuf);
if( pgno>0 && pgno<=pMain->nPage ){
if( 0==sqlite3BitvecTest(pMain->pWritable, pgno) ){
rc = sqlite3OsRead(pReal, aPage, pMain->nPagesize, iOff+4);
if( rc==SQLITE_OK ){
u32 cksum = genCksum(aPage, pMain->nPagesize);
assert( cksum==pMain->aCksum[pgno-1] );
}
}
sqlite3BitvecSet(pMain->pWritable, pgno);
}
iOff += (8 + pMain->nPagesize);
}
}

iOff = ((iOff + (nSector-1)) / nSector) * nSector;
}

finish_rjf:
start_ioerr_simulation(iSave, iSave2);
//sqlite3_free(aPage);
if( rc==SQLITE_IOERR_SHORT_READ ){
rc = SQLITE_OK;
}
return rc;
}


/*
** Write data to an jt-file.
*/
static int jtWrite(
sqlite3_file *pFile,
const void *zBuf,
int iAmt,
sqlite_int64 iOfst
){
int rc;
jt_file *p = (jt_file *)pFile;
if( p->flags&SQLITE_OPEN_MAIN_JOURNAL ){
if( iOfst==0 ){
jt_file *pMain = locateDatabaseHandle(p->zName);
assert( pMain );

if( iAmt==28 ){
/* Zeroing the first journal-file header. This is the end of a
** transaction. */
closeTransaction(pMain);
}else if( iAmt!=12 ){
/* Writing the first journal header to a journal file. This happens
** when a transaction is first started.  */
u8 *z = (u8 *)zBuf;
pMain->nPage = decodeUint32(&z[16]);
pMain->nPagesize = decodeUint32(&z[24]);
if( SQLITE_OK!=(rc=openTransaction(pMain, p)) ){
return rc;
}
}
}
if( p->iMaxOff<(iOfst + iAmt) ){
p->iMaxOff = iOfst + iAmt;
}
}

if( p->flags&SQLITE_OPEN_MAIN_DB && p->pWritable ){
if( iAmt<p->nPagesize
&& p->nPagesize%iAmt==0
&& iOfst>=(PENDING_BYTE+512)
&& iOfst+iAmt<=PENDING_BYTE+p->nPagesize
){
/* No-op. This special case is hit when the backup code is copying a
** to a database with a larger page-size than the source database and
** it needs to fill in the non-locking-region part of the original
** pending-byte page.
*/
}else{
u32 pgno = iOfst/p->nPagesize + 1;
assert( (iAmt==1||iAmt==p->nPagesize) && ((iOfst+iAmt)%p->nPagesize)==0 );
assert( pgno<=p->nPage || p->nSync>0 );
assert( pgno>p->nPage || sqlite3BitvecTest(p->pWritable, pgno) );
}
}

rc = sqlite3OsWrite(p->pReal, zBuf, iAmt, iOfst);
if( (p->flags&SQLITE_OPEN_MAIN_JOURNAL) && iAmt==12 ){
jt_file *pMain = locateDatabaseHandle(p->zName);
int rc2 = readJournalFile(p, pMain);
if( rc==SQLITE_OK ) rc = rc2;
}
return rc;
}

/*
** Truncate an jt-file.
*/
static int jtTruncate(sqlite3_file *pFile, sqlite_int64 size){
jt_file *p = (jt_file *)pFile;
if( p->flags&SQLITE_OPEN_MAIN_JOURNAL && size==0 ){
/* Truncating a journal file. This is the end of a transaction. */
jt_file *pMain = locateDatabaseHandle(p->zName);
closeTransaction(pMain);
}
if( p->flags&SQLITE_OPEN_MAIN_DB && p->pWritable ){
u32 pgno;
u32 locking_page = (u32)(PENDING_BYTE/p->nPagesize+1);
for(pgno=size/p->nPagesize+1; pgno<=p->nPage; pgno++){
assert( pgno==locking_page || sqlite3BitvecTest(p->pWritable, pgno) );
}
}
return sqlite3OsTruncate(p->pReal, size);
}

/*
** Sync an jt-file.
*/
static int jtSync(sqlite3_file *pFile, int flags){
jt_file *p = (jt_file *)pFile;

if( p->flags&SQLITE_OPEN_MAIN_JOURNAL ){
int rc;
jt_file *pMain;                   /* The associated database file */

/* The journal file is being synced. At this point, we inspect the
** contents of the file up to this point and set each bit in the
** jt_file.pWritable bitvec of the main database file associated with
** this journal file.
*/
pMain = locateDatabaseHandle(p->zName);
assert(pMain);

/* Set the bitvec values */
if( pMain->pWritable ){
pMain->nSync++;
rc = readJournalFile(p, pMain);
if( rc!=SQLITE_OK ){
return rc;
}
}
}

return sqlite3OsSync(p->pReal, flags);
}

/*
** Return the current file-size of an jt-file.
*/
static int jtFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
jt_file *p = (jt_file *)pFile;
return sqlite3OsFileSize(p->pReal, pSize);
}

/*
** Lock an jt-file.
*/
static int jtLock(sqlite3_file *pFile, int eLock){
int rc;
jt_file *p = (jt_file *)pFile;
rc = sqlite3OsLock(p->pReal, eLock);
if( rc==SQLITE_OK && eLock>p->eLock ){
p->eLock = eLock;
}
return rc;
}

/*
** Unlock an jt-file.
*/
static int jtUnlock(sqlite3_file *pFile, int eLock){
int rc;
jt_file *p = (jt_file *)pFile;
rc = sqlite3OsUnlock(p->pReal, eLock);
if( rc==SQLITE_OK && eLock<p->eLock ){
p->eLock = eLock;
}
return rc;
}

/*
** Check if another file-handle holds a RESERVED lock on an jt-file.
*/
static int jtCheckReservedLock(sqlite3_file *pFile, int *pResOut){
jt_file *p = (jt_file *)pFile;
return sqlite3OsCheckReservedLock(p->pReal, pResOut);
}

/*
** File control method. For custom operations on an jt-file.
*/
static int jtFileControl(sqlite3_file *pFile, int op, void *pArg){
jt_file *p = (jt_file *)pFile;
return sqlite3OsFileControl(p->pReal, op, pArg);
}

/*
** Return the sector-size in bytes for an jt-file.
*/
static int jtSectorSize(sqlite3_file *pFile){
jt_file *p = (jt_file *)pFile;
return sqlite3OsSectorSize(p->pReal);
}

/*
** Return the device characteristic flags supported by an jt-file.
*/
static int jtDeviceCharacteristics(sqlite3_file *pFile){
jt_file *p = (jt_file *)pFile;
return sqlite3OsDeviceCharacteristics(p->pReal);
}

/*
** Open an jt file handle.
*/
static int jtOpen(
sqlite3_vfs *pVfs,
const char *zName,
sqlite3_file *pFile,
int flags,
int *pOutFlags
){
int rc;
jt_file *p = (jt_file *)pFile;
pFile->pMethods = 0;
p->pReal = (sqlite3_file *)&p[1];
p->pReal->pMethods = 0;
rc = sqlite3OsOpen(g.pVfs, zName, p->pReal, flags, pOutFlags);
assert( rc==SQLITE_OK || p->pReal->pMethods==0 );
if( rc==SQLITE_OK ){
pFile->pMethods = &jt_io_methods;
p->eLock = 0;
p->zName = zName;
p->flags = flags;
p->pNext = 0;
p->pWritable = 0;
p->aCksum = 0;
enterJtMutex();
if( zName ){
p->pNext = g.pList;
g.pList = p;
}
leaveJtMutex();
}
return rc;
}

/*
** Delete the file located at zPath. If the dirSync argument is true,
** ensure the file-system modifications are synced to disk before
** returning.
*/
static int jtDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
int nPath = strlen(zPath);
if( nPath>8 && 0==strcmp("-journal", &zPath[nPath-8]) ){
/* Deleting a journal file. The end of a transaction. */
jt_file *pMain = locateDatabaseHandle(zPath);
if( pMain ){
closeTransaction(pMain);
}
}

return sqlite3OsDelete(g.pVfs, zPath, dirSync);
}

/*
** Test for access permissions. Return true if the requested permission
** is available, or false otherwise.
*/
static int jtAccess(
sqlite3_vfs *pVfs,
const char *zPath,
int flags,
int *pResOut
){
return sqlite3OsAccess(g.pVfs, zPath, flags, pResOut);
}

/*
** Populate buffer zOut with the full canonical pathname corresponding
** to the pathname in zPath. zOut is guaranteed to point to a buffer
** of at least (JT_MAX_PATHNAME+1) bytes.
*/
static int jtFullPathname(
sqlite3_vfs *pVfs,
const char *zPath,
int nOut,
char *zOut
){
return sqlite3OsFullPathname(g.pVfs, zPath, nOut, zOut);
}

/*
** Open the dynamic library located at zPath and return a handle.
*/
static void *jtDlOpen(sqlite3_vfs *pVfs, const char *zPath){
return g.pVfs->xDlOpen(g.pVfs, zPath);
}

/*
** Populate the buffer zErrMsg (size nByte bytes) with a human readable
** utf-8 string describing the most recent error encountered associated
** with dynamic libraries.
*/
static void jtDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
g.pVfs->xDlError(g.pVfs, nByte, zErrMsg);
}

/*
** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
*/
static void (*jtDlSym(sqlite3_vfs *pVfs, void *p, const char *zSym))(void){
return g.pVfs->xDlSym(g.pVfs, p, zSym);
}

/*
** Close the dynamic library handle pHandle.
*/
static void jtDlClose(sqlite3_vfs *pVfs, void *pHandle){
g.pVfs->xDlClose(g.pVfs, pHandle);
}

/*
** Populate the buffer pointed to by zBufOut with nByte bytes of
** random data.
*/
static int jtRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
return sqlite3OsRandomness(g.pVfs, nByte, zBufOut);
}

/*
** Sleep for nMicro microseconds. Return the number of microseconds
** actually slept.
*/
static int jtSleep(sqlite3_vfs *pVfs, int nMicro){
return sqlite3OsSleep(g.pVfs, nMicro);
}

/*
** Return the current time as a Julian Day number in *pTimeOut.
*/
static int jtCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
return sqlite3OsCurrentTime(g.pVfs, pTimeOut);
}

/**************************************************************************
** Start of public API.
*/

/*
** Configure the jt VFS as a wrapper around the VFS named by parameter
** zWrap. If the isDefault parameter is true, then the jt VFS is installed
** as the new default VFS for SQLite connections. If isDefault is not
** true, then the jt VFS is installed as non-default. In this case it
** is available via its name, "jt".
*/
int jt_register(char *zWrap, int isDefault){
g.pVfs = sqlite3_vfs_find(zWrap);
if( g.pVfs==0 ){
return SQLITE_ERROR;
}
jt_vfs.szOsFile = sizeof(jt_file) + g.pVfs->szOsFile;
sqlite3_vfs_register(&jt_vfs, isDefault);
return SQLITE_OK;
}

/*
** Uninstall the jt VFS, if it is installed.
*/
void jt_unregister(void){
sqlite3_vfs_unregister(&jt_vfs);
}

#endif
  }
#endif
#endif
}
